The intestinal epithelium is constantly exposed to foreign materials that can be either harmful or beneficial to the host. As a result, the intestinal immune system must strike a delicate balance between: 1) protective immune responses that are induced by intestinal pathogens or toxins and 2) avoidance of immune responses against both food antigens and the 1014 commensal beneficial microorganisms that normally reside in the gut. Disruption of either the protective responses or the tolerance responses can result in a wide array of disorders including, for example, infections, inflammation, food allergies, food hypersensitivity, inflammatory bowel disease, Crohn's disease, celiac disease, periodontal disease, rheumatoid arthritis, atherosclerosis and colon cancer.
The immunoregulatory network comprising the intestinal immune system changes with age. The network is poorly developed in human newborns and is established gradually over the first few years of life. The immaturity of the immune system plays a role in the prevalence of infections and food-related disorders in infants and young children. Conversely, the ability of the intestinal immune system to respond to new challenges declines in the elderly.
Gastrointestinal disorders, for example, infections, inflammatory disorders and food-related disorders such as food allergies, food intolerance or food hypersensitivity have a significant impact on the health and quality of life in both children and adults. Infectious gastroenteritis is the most common pediatric gastrointestinal disorder. About 1 billion episodes occur worldwide each year, most commonly in developing countries among children under 5 years of age. Worldwide death rates for infectious gastroenteritis average from 3 to 6 million children per year. In the United States, 25 to 35 million new cases occur annually, resulting in 300 to 400 deaths. In addition, infectious gastroenteritis in the US results in an estimated 200,000 hospitalizations and 1.5 million outpatient visits at a cost in excess of 1 billion dollars. Food-related disorders such as allergies also have a substantial effect on health or both children and adults. Symptoms of food allergies can vary depending upon the severity of the allergy and can range from a mild tingling sensation around the mouth and lips to life-threatening anaphylaxis. It is estimated that food allergies affect between 1-10% of the population in the U.S. The Center for Disease Control found that in 2007, approximately 3 million children under age 18 years (3.9%) were reported to have a food or digestive allergy in the previous 12 months. For some children, food allergies become less severe with age, for others, they remain a lifelong concern. Infants who suffer from allergy early in life may develop “allergic march.” For example, many individuals who have severe allergic reactions to cow's milk in infancy at risk for the development of asthma later in childhood. There are indications that the prevalence of food allergies is increasing worldwide.
Regardless of the etiology, gastrointestinal disorders not only adversely affect a child's health, but can have a serious impact on family economics, social interactions and school and parental work attendance. There is a continuing need for therapeutic strategies that promote gastrointestinal health, particularly in individuals who are risk for or who suffer from gastrointestinal disorders.